1. Field of the Invention
The invention relates to a straw for the conservation of small quantities of substances, notably biological substances, in particular biological liquids.
2. Description of the Prior Art
This type of straw, known under the term xe2x80x9cFrench strawxe2x80x9d, was disclosed for the first time in French patent No. 995 878.
The straws used up to now included a tripartite plug consisting of two pads of a fibrous substance enclosing a powder capable of being transformed in contact with a liquid into an impermeable gel or paste adhering to the wall of the tube, creating a tight stopper.
The tripartite plug straws we have developed and marketed give entire satisfaction. Nevertheless, a certain absorption of liquid contained in the straw may have been found, although very low.
There are also smaller tripartite plugs, but this solution does not solve the absorption problem either.
A solution that has been proposed to mitigate the aforesaid problem is to replace the tripartite plug with a ball of rigid plastics material or metal. This solution has not proved satisfactory because, although the absorption of liquid contained in the straw was reduced to zero, new unacceptable difficulties arose, the stopper no longer being at all impermeable to liquids.
One aim of the invention is to provide a straw incorporating closure means which, whilst being impermeable to liquids and permeable to gases, does not absorb any quantity of liquid.
Another aim of the present invention is to provide a straw allowing liquid to be absorbed through the closure means in a short time.
The invention achieves the above aims and provides a straw for the conservation of small quantities of substances, notably biological substances, comprising a segment of tube fitted internally at one end with closure means comprising a two-part plug comprising a microporous hydrophobic membrane and an insert through which there is a substantially coaxial orifice.
The insert is usually made of a material selected from elastomer materials, thermoplastics materials and thermoplastics elastomer materials.
In a preferred embodiment of the invention the insert has a substantially cylindrical external shape.
In one arrangement in accordance with the present invention the insert is tubular and its substantially coaxial orifice can be substantially cylindrical, conical or biconical, for example.
In one embodiment of the present invention the membrane surrounds the insert over some or all of its length.
In another embodiment of the present invention the membrane is substantially perpendicular to the longitudinal axis of the insert.
In a further embodiment of the present invention the insert is a two-part insert.
The insert can equally be molded, glued or welded to the membrane.
To facilitate its insertion into the straw the insert can have rounded ends.
The insert advantageously has a sealing segment on its external wall.
The microporous membrane used in the present invention preferably has a pore diameter in the range approximately 0.001 xcexcm to approximately 10 xcexcm and the diameter of the pores of the membrane is more preferably less than or equal to 0.2 xcexcm.
The membrane is made of a polymer material, for example, a material chosen from high-density polyethylene (PE-HD), polyamides, nitrocellulose, polyesters, phenol-formol resins (PF resins), perfluoroalkoxy resins (PFA resins) and fluorocarbon resins.
The polymer material of the membrane advantageously has a bubble point P greater than 6.105 Pa (6 bars) for 0.2 xcexcm.
The stopper of the straw of the present invention does not absorb liquids. It is permeable only to gases, in particular air, and is impermeable to liquids up to its intrusion pressure.
The other end of the straw, that is to say that not corporating the plug in accordance with the invention, normally remains open for filling it with the product to be conserved, which is generally a liquid.
To protect the product from contamination the open end is closed, for example welded closed, in particular by ultrasound or thermal welding, or using any other appropriate technique known to the skilled person.
Apart from the fact that it does not cause any absorption of the liquid contained in the straw, the plug of the invention has many advantages: it is not toxic, it can be sterilized and it can be frozen or heated without damage.
The plug of the invention is impermeable to liquids. It does not absorb either the diluent or the spermatozoids.
One advantage of the straw plug in accordance with the present invention is that it enables rapid filling of the straw.
The plug of the invention is particularly advantageous because it enables removal of only some of the liquid contained in the straw whilst conserving the straw for subsequent use. This has not been possible with the prior art tripartite plug.
Another advantage of the invention is that the non-absorbent plug authorizes good adhesion to the parts of the straw, so avoiding the loosening that is well known when the tripartite plug is used.
Another advantage of the invention is that, because of its porosity, the plug has a filter effect enabling use in a more or less sterile manner.
Another advantage of the invention is that the product can be re-absorbed with the same straw.
Another advantage of the two-part plug of the present invention is that the straw can be marked by the color of the insert. This provides a xe2x80x9ccolor codexe2x80x9d without having to use colored straws.
The present invention will be described in more detail with reference to FIGS. 1 through 9 of the accompanying drawings.